Boreholes or wellbores for hydrocarbon (oil and gas) production, as well as for other purposes, are usually drilled with a drill string that includes a plurality of interconnected tubular members (individually referred to as segments of drill pipe), having a drilling assembly which includes a drill bit attached to the bottom end thereof. The drill bit is rotated to shear or disintegrate material of the rock formation to drill the wellbore. The drill string often includes tools or other devices that are in operation located downhole and are therefore remotely activated and deactivated during drilling operations. Such tools and devices include, for example, reamers, stabilizers, steering tools for steering the drill bit, and formation testing devices.
The drill string is often drivingly rotated by the application of torque and rotation at the surface, so that a tubular wall of the drill string (also referred to herein as the drill pipe) is rotated at a common speed. While relatively high rotational speeds are often useful in some parts of the drill string (e.g., adjacent the drill bit, to agitate cuttings to promote efficient evacuation thereof), structural features in other parts of the drill string can often limit the speed at which the drill string can be operated safely.